Photon counting CT detectors suffer from the so-called pile-up effect. In the extreme case of very high flux (i.e. radiation impinging on the detector), complete paralysis appears where the detector is fully saturated and does not output any counts at all. Unfortunately, this may happen consistently for all detector pixels which measure only a very small ray length of the radiation beam through the object of examination, e.g. a patient. In other words, all projections may be truncated, particularly on both sides where the radiation does not penetrate the object or only a thin part of the object. This type of truncated projections is quite undesired for reconstruction of images. In particular, quantitative reconstruction becomes almost impossible.
Several attempts have been made to overcome the problem of this pile-up effect and of truncated projections. For instance, WO 2013/093726 A1 discloses a detection apparatus comprising a pile-up determining unit for determining whether detection signal pulses being indicative of detected photons are caused by a pile-up event or by a non-pile-up event, wherein a detection values generating unit generates detection values depending on the detection signal pulses and depending on the determination whether the respective detection signal pulse is caused by a pile-up event or by a non-pile-up event. The detection signal pulse if caused by pile-up events may be rejected while generating the detection values. This allows for an improved quality of the generated detection values.